The Pollen Monitor BAA500 is the first of a future line of fully-automated analytical devices for monitoring airborne particles or particles transported in liquids. It combines automated sampling, digital image processing and analysis, and archival storage of the sample carriers in one single and autonomous unit.

The Helmut Hund GmbH of Wetzlar, Germany, has a 30-year experience in particle-measuring technology and microscopy, and both disciplines are combined in the BAA500. During the whole of the development process, high value was set on robustness, fully-automated long-term operability and user friendliness. The BAA500 is designed for a one-month autonomous operation.

The BAA500 employs the only effective method for discriminating different pollen taxa that is already used by human pollen counters: the analysis of morphologic properties. The pollen are separated from an airstream of 6 m³/h (max.) with a virtual impactor particularly designed for the typical pollen sizes: It utilizes the inertia of the pollen grains to deposit those with a diameter of between 5 µm and 100 µm on a sample carrier of about 10 mm diameter. The sample carriers are coated with a special gel to which the pollen grains stick when they reach the carrier.

The sample carriers are stored in a storage magazine and from here, they are transferred to a rotary table. After the sampling process, the carrier is transported to a heating station where the pollen grains sink into the gel and are thus hermetically sealed for later archiving. In the next step, the rotary table transports the sample carriers to a 3D scanner. This scanner is vibration-isolated from the rest of the handling system. In this highly precise positioning system, the sample is scanned in three dimensions under an inverted microscope with LED illumination, CCD camera and subsequent image processing system. When scanning the whole of the sample area, the scanner takes a total of 350 image stacks of 70 single images each. The z distance between two images of a stack is 1.5 µm. The image files are stored on a hard drive, and during the scanning process, the next sample carrier is probed already. The scanned sample carrier is finally transferred to the archive magazin that can hold the samples of a complete month.

The image analysis system runs on an additional computing system. Parallel to the sampling process, it picks up the images from the hard drive, discriminates pollen from other airborne particles (dust, tyre abrasion or diesel exhaust particulates etc.) and classifies them according to their morphological properties. The result is always a table containing the pollen taxa and their respective pollen counts. Every hour, this table is electronically transferred to, e.g., meteorological services. Eventually, interested allergic persons can be informed about the daily pollen count as quickly as never before, and this enables them to protect themselves early and more effectively.